RFID technology is often used to determine which tagged items are within the reading field of an RFID reader. A tagged item is typically identified by a simple ID stored in the RFID tag associated with the item. The RFID tag can also include additional information relative to the tagged item.
Knowing the position of a tagged item, and being able to read the data stored in the RFID tag attached to the item, is useful, for example, for inventory and/or retrieval purposes. Currently, position determination is provided by active (i.e., battery powered) RFID tags. Unfortunately, active RFID tags cannot be used in conjuction with numerous small items all located in a small area.
When many small items equipped with RFID tags are in the reading field of an RFID reader, it is necessary to use an “anti-collision” mechanism to read each individual RFID tag. Although many anti-collision mechanisms exist, they are designed to read all of the RFID tags present in the reading field of an RFID reader, and are incapable of selectively reading an RFID tag located at a predetermined position. To this extent, it is not possible to only read the information of an RFID tag in a given (geographical) position, without being disturbed by information sent by other RFID tags in the reading field of an RFID reader.